In contrast, speakers of a language are usually not aware of allophonic variation they tend to perceive different allophones of a single phoneme as the same sound for example, most speakers of English do not realize that the"t" sounds in till still and bitter are slightly different because mentally they produce and hear phonemes not allophones (Fromkin et al. 2007). Moreover, spelling systems usually provide symbols for phonemes, not allophones(Stewart, Jr. and Vaillette 2001). As a result, there are no separate letters for[t], [t], and [r] in English; the three allophones are spelled with the same letter t Like the English phoneme/t/, all phonemes in a language have their related allophones. In some cases, a phoneme has only one allophone; it is pronounced exactly the same in all environments. When a phoneme is associated with more than one, the allophones must be phonetically similar, that is, they must share most phonetic features. For example, while [t], and [r] differ in aspiration and voicing they aer produced at the same place and by the same manner of articulation they all are described as alveolar stops. Most phonemes have more than one allophone, and the distribution of each of their allophones is consistent. Therefore, pronunciation is not random process; it is systematic and rule-governed(Fromkin et al. 2007). In every language, a particular sound is always pronounced by its speakers in a specific way when it occurs in a certain phonetic context.